Two maternal effect mutations with drastic effects on polarity in early embryos have been mapped very close to one another and both fall into a small deficiency interval. One mutant, Bicaudal-b (Bic-b), is a dominant and lays bicaudal eggs. Females homozygous for the other mutation, dorsal (dl), produce embryos that lack all ventral structures. We propose a number of genetic and molecular studies on the organization of these genes, their time and mode of action, and their role and importance in the establishment of polarity in the developing egg and during embryogenesis. We plan to study the interaction of these genes with other genes involved in polarity decisions. Transformation experiments will be done first to study how the expression of these genes is controled and second to learn more about their function. We also plan to isolate antibodies directed against Bic-B and dl gene products and these will be used to study the distribution and intracellular localization of the Bic-b and dl gene products.